Special relativity is a theory of the structure of space and time. It was introduced by Albert Einstein’s 1905 paper “On the Electrodynamics of Moving Bodies.” Special relativity is based on two postulates which are contradictory in classical mechanics:
1. The law of physics is the same for all observers in uniform motion relative to one another.
2. The speed of light in a vacuum is the same for all observers, regardless of their relative motion of the source of the light. General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field (for example when standing on the surface of the Earth) are physically identical. The upshot of this is that free fa
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ll is inertial motion; an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as is the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories initially moving objects cannot accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first proposed that space time is curved. In 1915, he devised the Einstein field equations which relate the curvature of space time with the mass, energy, and momentum within it. The implacations of Special relativity rage from the conseptual understanding of all celestrial bodies to making citys with nucular power or destroying them with nucular arms as well as taking a trip to the future out of science fiction. Einstein determained that if light moved away from you at the same speed no matter how fast you were going something had to be giving away. If It had been established that nothing can move faster than the speed of light what is to stop someone say on a futureistic spaceship traveling at 99.99% the speed of light from running as fast as they can inside the spaceship breaking the light speed barrier. The answer: Time, time slows down inside the space ship as it approches near-light speeds to act as a natural speed check protecting the cosmic speed limit. Since time is moving slower inside the spacship (even though it would feel like it was passing normally by anyone on board) than outside the space ship the longer this speed was mantained the futher into the future the passangers would go.
Vocabulary
1.Special theory of relativity: The theory describes how time is affected by motion in space at constant velocity, and how the mass and energy are related.
2.Space-time: The physical reality that exists within the four dimensional continuum..
3.Time dilation: The apparent loss of time by moving a clock as observed by a stationary observer.
4.First postulate of special relativity: All the laws of nature are the same in all uniformly moving frames of references.
5.Second postulate of special relativity: The speed of light in empty space will always have the same value regardless of the motion of the source or the motion of the observer.
6.Postulates: Something that is taken as self-evident or assumed without proof as making a basis for reasoning.
7.Twin Trip: A dramatic illustration of time dilation is afforded by the identical twins, one astronuat takes a high-speed round-trip journey while the other stays home on earth.
8.Recedes: To go away or retreat.9.Frequently: Often;many times.
10.Earthbound: Firmly set or attached to the earth.
Space-Time
Einstein’s theories of relativity tell us that Space, for example - the room you are sitting in, and Time, the minutes that tick away on your watch, are all part of a single physical entity, the Space-time Continuum. Space-time has four dimensions, roughly corresponding to east-west, north-south, up-down, and past-future. We can drive from east to west, north to south, and go up and down mountains. While we are driving in any direction we are always driving from our past to our future – that is basically why space and time are linked, we can’t move through space without moving through time! Before Einstein, Isaac Newton shared the popular belief that both absolute time and absolute space exist. Newton believed that the grid that defined absolute space was undetectable, but that there is a universal time that ticks away for all observers in all locations, and that universal time can be accurately measured by clocks. If it is 5 o'clock on planet earth, it is simultaneously 5 o'clock on the most distant star. Similarly, Newton believed that absolute space exists that can be measured using the same yardstick (meter-stick) anywhere in the cosmos, a mile measures the same distance anywhere on Earth and on any distant star as it does where you are standing right now.
There are lots of problems with this idea, experimental observations simply do not support the conclusion that absolute time and absolute space exist. An answer that says that space and time are fixed seems reasonable, but it leaves many questions unanswered. In 1905 Einstein published his theory of special relativity, which introduced the then radical idea that different observers see the same event occurring at different times and places. For example, Bill and Sally may see two firecrackers that they ignite explode at exactly the same time, while Jane (in motion at a distance) may see one of the two firecrackers explode a few seconds before the other one.Einstein used the concept of relationships between frames of reference to explain how these "crazy" observations are real and actually doing occur. Frames of reference may be thought of as invisible "coordinate map grids", like the letters and numbers on the sides of roadmaps, attached to every observer so that the observer can measure the position of surrounding objects. [1]
Motion Is Relative
The laws of physics which apply when you are at rest on the earth also apply when you are in any reference of frame.
All Motion is relative to the observer or to some fixed object. When you see a car driving by, it is moving with respect to you. If you are going in a car that is going the same speed, the other car will not be moving with respect to you. But both cars are moving with respect to the ground.
POINT OF REFERNECE
In talking about Motion, it is important to indicate your point of reference. Instead of the moving automobiles, it is usually assumed that both cars go with respect to the ground.But in some cases there are some situations that where the speed or velocity may be an respect with an other object or the observer.
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For example, suppose that a car was traveling at 60miles per hour and it hit another car, but there was hardly a dent. The reason for that is that the car was traveling the same direction at 59 mph, so the car was goingnly 1 mph with respect to the other car when it hit it.
SUN LOOKS LIKE ITS MOVING IN THE SKY
Another exampleof relative motion is how the sun appears to move across the sky, when the the earth is actually spinning and cuasing the apparent motion.
Usually, we consider motion with respect to the ground or the Earth. Within the universe there is no real fixed point. The basis for Einstein's Theory of Relativity is that all motion is relative to what you define as a fixed point. [2]
The Speed of Light Is Constant
The speed of light is a physical constant. Its value is exactly 299,792,458 meters per second, often approximated as 300,000 kilometers per second or 186,000 miles per second (see the table on the right for values in other units). It is the speed of electromagnetic radiation in vacuum, where there are no atoms, molecules or other types of matter that can slow it down.
For much of human history, it was not known whether light was transmitted instantaneously or simply very quickly. In the 17th century, Ole Roomer first demonstrated that it travelled at a finite speed by studying the apparent motion of Jupiter's moon Io. By 1975, the speed of light was known to be 299,792,458 m/s with a relative measurement uncertainty of 4 parts per billion. In 1983, the meter was redefined in the International System of Units (SI) as the distance travelled
Image courtesy of The Blog
by light in vacuum in 1⁄299,792,458 of a second. As a result, the numerical value of c in meters per second is now fixed exactly by the definition of the meter.
According to the theory of special relativity, c connects space and time in the unified structure of space-time, and its square is the constant of proportionality between mass and energy (E = mc2). In any inertial frame of reference, independently of the relative velocity of the emitter and the observer, c is the speed of all mass less particles and associated fields, including all electromagnetic radiation in free space, and it is believed to be the speed of gravity and of gravitational waves. It is an upper bound on the speed at which energy, matter, and information can travel, as surpassing it "would lead to the destruction of the essential relation between cause and effect. Its finite value is a limiting factor in the speed of operation of electronic devices. [3]
The First Postulate of Special Relativity
The first Postulate of the theory of special relativity is not too hard to swallow.The laws of physics hold the true for all frames of references. This is the simplest of all relativistic concepts to grasp.The physical laws help us understand how many and why our enviroment reacts the way it does. It also allows us to predict events and their outcomes.Consider a yardstick and a cement block.If you measure the length on the block, you will get the same result regardless of whether you are standing on the ground or riding a bus. Next, measure the time it takes a pendulumto make full swings from its resting point.Again, you will get the same result whether you are standing on the ground or riding a bus.The differences in the results of why the experiments occur because the laws of physics remain the same for all frames of references. For example, if we crash into each other, we will find that the energy was conserved for the collision regardless of whether we were in one of the cars or standing on the side walk.
The Second Postulate of Special Relativity
Light is always propagated in empty space with a definite velocity, which is independent if the state of motion of emitting body.
This is the expression for a universial continuum independent of the frame of reference a body occupies. However, the postulate is later modified to, "Any ray of light moves in the " stationary" system of co-ordinates with the determined velocity c whether the ray is emitted by a stationary or by a moving body.
Table of Contents
Special Relativity
Special relativity is a theory of the structure of space and time. It was introduced by Albert Einstein’s 1905 paper “On the Electrodynamics of Moving Bodies.” Special relativity is based on two postulates which are contradictory in classical mechanics:
1. The law of physics is the same for all observers in uniform motion relative to one another.
2. The speed of light in a vacuum is the same for all observers, regardless of their relative motion of the source of the light.
General relativity is a theory of gravitation developed by Einstein in the years 1907–1915. The development of general relativity began with the equivalence principle, under which the states of accelerated motion and being at rest in a gravitational field (for example when standing on the surface of the Earth) are physically identical. The upshot of this is that free fa
Vocabulary
1.Special theory of relativity: The theory describes how time is affected by motion in space at constant velocity, and how the mass and energy are related.
2.Space-time: The physical reality that exists within the four dimensional continuum..
3.Time dilation: The apparent loss of time by moving a clock as observed by a stationary observer.
4.First postulate of special relativity: All the laws of nature are the same in all uniformly moving frames of references.
5.Second postulate of special relativity: The speed of light in empty space will always have the same value regardless of the motion of the source or the motion of the observer.
6.Postulates: Something that is taken as self-evident or assumed without proof as making a basis for reasoning.
7.Twin Trip: A dramatic illustration of time dilation is afforded by the identical twins, one astronuat takes a high-speed round-trip journey while the other stays home on earth.
8.Recedes: To go away or retreat.9.Frequently: Often;many times.
10.Earthbound: Firmly set or attached to the earth.
Space-Time
Einstein’s theories of relativity tell us that Space, for example - the room you are sitting in, and Time, the minutes that tick away on your watch, are all part of a single physical entity, the Space-time Continuum. Space-time has four dimensions, roughly corresponding to east-west, north-south, up-down, and past-future. We can drive from east to west, north to south, and go up and down mountains. While we are driving in any direction we are always driving from our past to our future – that is basically why space and time are linked, we can’t move through space without moving through time! Before Einstein, Isaac Newton shared the popular belief that both absolute time and absolute space exist. Newton believed that the grid that defined absolute space was undetectable, but that there is a universal time that ticks away for all observers in all locations, and that universal time can be accurately measured by clocks. If it is 5 o'clock on planet earth, it is simultaneously 5 o'clock on the most distant star. Similarly, Newton believed that absolute space exists that can be measured using the same yardstick (meter-stick) anywhere in the cosmos, a mile measures the same distance anywhere on Earth and on any distant star as it does where you are standing right now.
There are lots of problems with this idea, experimental observations simply do not support the conclusion that absolute time and absolute space exist. An answer that says that space and time are fixed seems reasonable, but it leaves many questions unanswered. In 1905 Einstein published his theory of special relativity, which introduced the then radical idea that different observers see the same event occurring at different times and places. For example, Bill and Sally may see two firecrackers that they ignite explode at exactly the same time, while Jane (in motion at a distance) may see one of the two firecrackers explode a few seconds before the other one.Einstein used the concept of relationships between frames of reference to explain how these "crazy" observations are real and actually doing occur. Frames of reference may be thought of as invisible "coordinate map grids", like the letters and numbers on the sides of roadmaps, attached to every observer so that the observer can measure the position of surrounding objects. [1]
Motion Is Relative
The laws of physics which apply when you are at rest on the earth also apply when you are in any reference of frame.
All Motion is relative to the observer or to some fixed object. When you see a car driving by, it is moving with respect to you. If you are going in a car that is going the same speed, the other car will not be moving with respect to you. But both cars are moving with respect to the ground.
POINT OF REFERNECE
In talking about Motion, it is important to indicate your point of reference. Instead of the moving automobiles, it is usually assumed that both cars go with respect to the ground.But in some cases there are some situations that where the speed or velocity may be an respect with an other object or the observer.
For example, suppose that a car was traveling at 60miles per hour and it hit another car, but there was hardly a dent. The reason for that is that the car was traveling the same direction at 59 mph, so the car was goingnly 1 mph with respect to the other car when it hit it.
SUN LOOKS LIKE ITS MOVING IN THE SKY
Another exampleof relative motion is how the sun appears to move across the sky, when the the earth is actually spinning and cuasing the apparent motion.
Usually, we consider motion with respect to the ground or the Earth. Within the universe there is no real fixed point. The basis for Einstein's Theory of Relativity is that all motion is relative to what you define as a fixed point. [2]
The Speed of Light Is Constant
The speed of light is a physical constant. Its value is exactly 299,792,458 meters per second, often approximated as 300,000 kilometers per second or 186,000 miles per second (see the table on the right for values in other units). It is the speed of electromagnetic radiation in vacuum, where there are no atoms, molecules or other types of matter that can slow it down.
For much of human history, it was not known whether light was transmitted instantaneously or simply very quickly. In the 17th century, Ole Roomer first demonstrated that it travelled at a finite speed by studying the apparent motion of Jupiter's moon Io. By 1975, the speed of light was known to be 299,792,458 m/s with a relative measurement uncertainty of 4 parts per billion. In 1983, the meter was redefined in the International System of Units (SI) as the distance travelled
According to the theory of special relativity, c connects space and time in the unified structure of space-time, and its square is the constant of proportionality between mass and energy (E = mc2). In any inertial frame of reference, independently of the relative velocity of the emitter and the observer, c is the speed of all mass less particles and associated fields, including all electromagnetic radiation in free space, and it is believed to be the speed of gravity and of gravitational waves. It is an upper bound on the speed at which energy, matter, and information can travel, as surpassing it "would lead to the destruction of the essential relation between cause and effect. Its finite value is a limiting factor in the speed of operation of electronic devices. [3]
The First Postulate of Special Relativity
The first Postulate of the theory of special relativity is not too hard to swallow.The laws of physics hold the true for all frames of references. This is the simplest of all relativistic concepts to grasp.The physical laws help us understand how many and why our enviroment reacts the way it does. It also allows us to predict events and their outcomes.Consider a yardstick and a cement block.If you measure the length on the block, you will get the same result regardless of whether you are standing on the ground or riding a bus. Next, measure the time it takes a pendulumto make full swings from its resting point.Again, you will get the same result whether you are standing on the ground or riding a bus.The differences in the results of why the experiments occur because the laws of physics remain the same for all frames of references. For example, if we crash into each other, we will find that the energy was conserved for the collision regardless of whether we were in one of the cars or standing on the side walk.
The Second Postulate of Special Relativity
Light is always propagated in empty space with a definite velocity, which is independent if the state of motion of emitting body.
This is the expression for a universial continuum independent of the frame of reference a body occupies. However, the postulate is later modified to, "Any ray of light moves in the " stationary" system of co-ordinates with the determined velocity c whether the ray is emitted by a stationary or by a moving body.
References